Electronic device for controlling the brakes of a vehicle

ABSTRACT

The device comprises a magnetic inertia block connected to return means fixedly mounted onto either a pulled vehicle or a pulling vehicle, magnetic transducer positioned adjacent the magnetic inertia block and connected to a current source, treating means connected to said magnetic transducer, output of said treating means being connected to the brakes of the vehicle.

BACKGROUND OF THE INVENTION

The present invention relates to an electronic device for controllingthe brakes of a vehicle and is particularly provided for the control ofelectro-magnetic brakes for a towed or pulled vehicle.

Though the device according to the invention uses an inertia block, saiddevice is different from all the inertia and generally pendular devicespresently used in relation with the braking of pulled vehicles.Particularly, contrary to already known devices, it does not require useof incandescent or infra-red lamps which have a very limited life-time,nor photosensitive cells able to have an important drift depending onthe weather and other ambient conditions.

SUMMARY OF THE INVENTION

The invention has for its purpose a device providing an electric currentwhich is substantially proportional to the instantaneous deceleration orbraking acceleration of the vehicle, said current being eitherapplicable directly to electromagnetic brakes, or as input to atransducer having an output as a hydraulic or pneumatic signal, saidsignal being then applied to the hydraulic or pneumatic brakes.

According to the invention, the device for controlling the brakes of apulled vehicle which is towed by a pulling vehicle comprises:

A magnetic inertia block;

Return means fixedly mounted on one of the two vehicles, said meansbeing fixed to said magnetic inertia block for permitting movementsubstantially in parallel to the longitudinal axis of said one of thevehicles when the vehicle is decelerated and returning to an originalposition at end of the deceleration, whereby upon braking thedeceleration causes the magnetic inertia block to continue its motionwhile driving the return means;

A MAGNETIC TRANSDUCER PLACED IN VICINITY OF THE MAGNETIC INERTIA BLOCK,IN PARALLEL WITH ITS DIRECTION OF MOTION, AT LEAST ONE ELECTRICCHARACTERISTIC OF SAID MAGNETIC TRANSDUCER BEING MODIFIED IN CONNECTIONWITH THE EXPOSURE OR COVERING BY THE MAGNETIC INERTIA BLOCK OF THESENSITIVE OR ACTIVE PORTION OF THE TRANSDUCER, SAID TRANSDUCER BEINGELECTRICALLY CONNECTED TO A CURRENT SOURCE THROUGH A CONTROL SWITCH;

TREATING MEANS CONNECTED TO SAID MAGNETIC TRANSDUCER FOR THE TREATMENTOF SAID MODIFIED ELECTRIC CHARACTERISTIC, OUTPUT OF SAID TREATING MEANSBEING CONNECTED TO THE BRAKES OF THE VEHICLE.

Other objects and features of the invention will be apparent from thefollowing description and claims and illustrated in the accompanyingdrawings, which disclose, by way of example, the principle of theinvention, and the best mode contemplated for carrying it out.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic perspective view of the device of theinvention.

FIG. 2 represents a variant of one of the characteristic features of thedevice of FIG. 1.

FIG. 3 is an electric diagram of the device of the invention.

FIG. 4 is a curve explaining the operation of the device of theinvention.

FIG. 5 shows a variant of one of the characteristic features of thedevice of FIG. 1.

FIGS. 6a, 6b and 6c are block diagrams of variant parts of the device ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, there is shown a plate P made of electrically insulatingmaterial on which have been placed the various components of the presentdevice as they appear while connected in FIG. 3, in which the sameelements bear the same references.

A resilient blade L is placed on the plate P through an angle plate or asquare E and at the end of the blade there is fixed, for example byglueing, a magnetic inertia block M of any shape and nature, and ifdesired a non-magnetic inertia block m. The diagrammatic perspectiveview of FIG. 1 also shows two elements R₁ and R₂, of which one at least,the element R₁ is a magnetic transducer in the form of amagnetoresistance or of a Hall effect cell, while the element R₂ may besimilar to element R₁ or may be a mere resistance. The device furthercomprises standard resistors R₃, R₄ R₆ with R₃ and R₆ being adjustableresistances. All the resistive elements are connected together, asbetter seen in FIG. 3, through an operational amplifier Am to a powertransistor T, the output of the transistor T constituting the outputterminals S₁ and S₂ of the device of which the input terminals are E₁and E₂.

The plate P is fixedly mounted either on the pulling vehicle or on thepulled vehicle to control the brakes of the pulled vehicle; the arrow Fof FIG. 1 showing the travelling direction of the vehicle, parallel tothe axis of said vehicle.

It is then obvious that the magnetic inertia block M will, under theinfluence of a deceleration or braking acceleration, move with respectto its position at rest, in a way substantially parallel to the axis ofthe vehicle. Upon its motion, the magnetic inertia block will thusvariably cover or exposure the magnetic transducer R₁.

In the variant of FIG. 2, the magnetic inertia block M has beenrepresented connected to springs s₁ and s₂ whose free ends are fixedlymounted to the plate P. The general direction of the springs s₁ and s₂is that of the axis of the vehicle, parallel to the arrow F. Then in theevent of a deceleration, the inertia block will variably cover or exposethe magnetic transducer R₁ as explained hereinabove in relation to FIG.1.

As known, a magnetic transducer is a component of which at least oneelectric characteristic is modified when a magnetic body comes close toits sensitive or active portion while exposing or covering said portion.Practically, the magnetic transducer is either a magneto-resistance or aHall effect cell. However, for sake of simplifying the circuit, only theuse of magneto-resistance is considered hereinbelow, and themagneto-resistance R₁ is placed on the plate P in such a way that it isinfluenced as soon as the inertia block will move.

It should be noted from the above disclosure, that when a decelerationoccurs, the magnetic inertia block M tends to keep on moving and drivesthe resilient blade or the spring in its motion. The magnetic inertiablock M thus comes close to the magneto-resistance R₁ whose resistanceincreases all the more that the magnetic inertia block is close.Therefore, the relative motion of the magnetic inertia block M and themagneto-resistance R₁ is all the more important commensurate with thefact that the deceleration is important. When the decelerationdecreases, the resilient blade or the spring brings back the magneticinertia block M towards its original or rest position.

It thus appears that with the use of a treatment means interpreting theresistance changes of the magneto-resistance at the moment of thedeceleration, there can be formed an electric signals substantiallyproportional to the instantaneous deceleration of the vehicle on whichthe brakes must be applied, and as shown in FIG. 6a said signals can bedirectly applied to electro-magnetic brakes or yet sent towards anelectrical-hydraulic or electrical/pneumatic transducer for the controlof hydraulic or pneumatic brakes (FIGS. 6b and 6c respectively). In FIG.3, the elements of FIG. 1 have then been shown as connected for thecontrol of electro-magnetic brakes.

In FIG. 3, the magneto-resistance R₁ is inserted in the arms of aWheatstone bridge having as other resistances R₂, R₃ and R₄. Themagnetic mass M is shown in front of the magneto-resistance R₁ and thearrows f illustrate the motion of the magnetic mass. The resistance R₂is adjustable for setting the zero of the Wheatstone bridge in restposition of the inertia block M. The Wheatstone bridge is thus shownconnected at E₁ to the terminals of a stop lamp L₂ which becomeslightened when the driver of the vehicle pushes on the brake pedalF_(f). Actually, at that very moment, the contact K or stop switch isclosed through a connection M_(m), for example a mechanical connection,and, through the battery B_(at) of the vehicle, the lamp L_(s) ispowered as well as the whole device.

The common points A and B to the resistances R₁ -R₂ on one hand, and R₃-R₄ on the other hand, constitute the ends of a diagonal of the bridgeand are connected through a resistance R₅ to an integrated amplifierA_(m) which is also connected to the terminals of the lamp L_(s). Theresistance R₆ connected in feed-back relation between the input and theouput of the amplifier enables to adjust the gain of the device.

The output of the amplifier A_(m) is connected to the base b of thepower transistor T whose collector is connected to the input E₁ of thedevice which is thus at the potential of the lamp L_(s) and whoseemitter constitutes the output terminal S₁ and is connected to one endof a coil C of the electro-magnetic brakes of the pulled vehicle, adiode D being connected across the coil C and the other end of the coilC being connected to the output terminal S₂ of the device.

The above described device operates as follows:

When the driver of the pulling vehicle pushes on the brake pedal, thestop switch is closed and through a connection (not shown) operatingdirectly the brakes of said vehicle, the pulling vehicle slows down ordecelerates and the deceleration is transmitted to the pulled vehicle.At that moment, the stop switch which is closed supplies the currentfrom the battery to the stop lamp L_(s) and also to the present device.As the deceleration has started, the inertia block M has come closer tothe magneto-resistance R₁, then the resistance of R₁ has increased.Then, the potential in A with respect to the potential in B decreases,thus the voltage increases at the output of the integrated amplifierA_(m).

Practically in an example of embodiment, the potential differencebetween A and B is within the range of 0.2 to 0.4 volt for amagneto-resistance having an initial resistance at rest of 200 ohms andwith a magnetic inertia block of about 0.5 cm3 of which the North orSouth pole passes within 1 mm of the magneto-resistance suitablyconnected for operative purposes.

If R₅ is far more important than R₁ the amplifier gain A_(m) is givenby - R₆ /R₅ and can be adjusted by means of the adjustable resistanceR₆.

The signal at the output of the amplifier is amplified by the transistorT to be applied to the coil C of the brakes.

Since device has to be operational in a large range of temperature andin view of making the output signal independent from the ambienttemperature, it is advantageous to replace R₂ by anothermagneto-resistance. Said modification gives a good stability on all therange from 0° to 60° C. It is even possible to make the secondmagneto-resistance R₂ active; in such a case, R₂ is placed under theelement in rest position as shown in FIG. 1. There is thus obtained adifferential working operation (difference between the instantaneousvalues of R₁ and R₂). The signal so obtained between A and B is thentwice as important. The form of the voltage which is obtained across thecoil C is shown as an example in FIG. 4.

Referring now to FIG. 4, the deceleration has been shown in abscissa andthe corresponding voltage existing at the terminals of the coil C hasbeen shown in ordinate. Then, for a braking acceleration or decelerationabout 1m/s2, the voltage across the coil C is about 2 volts while thevoltage is 12 volts for a deceleration of about 6m/s2, the variation ofthe voltage across the coil C varying substantially linearly betweenthese limits. The pulled vehicle is thus braked more stronglycommensurate with the deceleration caused by the braking of the pullingvehicle being important.

Regarding the external or physical aspect of the device of the presentinvention, its electronic portion is housed in a casing placed in themost suitable area of a pulled vehicle as a trailer or a caravan, whileits position has no influence on the operation of the device. The casingcan also be placed on the pulling vehicle.

The present invention thus controls the braking of a trailer or anypulled vehicle without requiring the use of the control circuit of thepulling vehicle. Besides, since the system is not really pendular, it isnot significally influenced by a slope of 10° to 20° of the vehicle onwhich is fixed the device, which prevents the requirement for tediousadjustments of the zero found in all the other existing apparatus.

Two fundamental arrangements of the blade L acting as a spring can befound. The blade L can be placed either vertically or horizontally. Itshould be noted that the vertical position does not require the blade toact as a spring if the bearing point is hingedly mounted (see FIG. 5:rod r movable about a horizontally placed spindles). The return to therest position is then obtained by the gravity action and a spring effectproduced either by the elastic blade L of FIG. 1 or by the springs ofFIG. 2 is not required in such a case.

The present invention is not restricted to the embodiment shown anddescribed in detail, for various modifications thereof can moreover beapplied thereto without departing from the scope of the presentinvention as claimed. Especially, the voltage applied to the device canbe directly sent to the circuit from a d.c. supply source of suitablevalue and by means of a hand-control placed on the instrument panelwithin easy reach of the driver and constituting an emergency control.

I claim:
 1. A device for controlling the brakes of a pulled vehicletowed by a pulling vehicle, said device comprising a current source, acontrol switch connected to said current source, magnetic transducersmounted on one of said vehicles and spaced along a line parallel to thelongitudinal axis of said one vehicle and connected to said currentsource through said control switch, said transducers producing an outputsignal, said transducers being magneto-resistances interconnected in twoarms of a four-arm diagonal bridge having the current source connectedto one diagonal, a signal treating means including the other two armsand the other diagonal of said bridge for receiving said output signal,said signal treating means controlling said brakes, setting means tobalance said bridge, a magnetic inertia block, spring means for mountingsaid block on said one vehicle between said transducers for movementsubstantially parallel to the longitudinal axis of said one vehicle sothat said block moves into closer proximity to one of said transducersand farther from the other of said transducers to unbalance the bridgeand to modify at least one electric characteristic of said output signalin response to deceleration of said one vehicle to give an output signalsubstantially proportional to the instantaneous deceleration of avehicle to control the brakes of a pulled vehicle.
 2. A device asclaimed in claim 1, in which said two transducers act to compensate fortemperature changes.